<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Document</title>
</head>

<body>
  <form>
    <input type="file" name="avatar" accept="image/*" placeholder="请选择头像" />
    <button>上传文件</button>
  </form>
  <img src="" alt="" class="avatar" style="width: 500px" />
</body>
<script src="./js/axios.js"></script>
<script>
  const form = document.querySelector('form');
  const img = document.querySelector('.avatar');

  form.addEventListener('submit', async function (e) {
    e.preventDefault()
    const fd = new FormData(form)
    console.log(fd.get('avatar'));
    const {data:res} = await axios.post('http://ajax-api.itheima.net/api/file', fd)
    img.src = res.data.url
  })
</script>

</html>